Process and plant for building tyres for vehicle wheels

ABSTRACT

During building of tyres, at least one first forming drum is employed which has a deposition surface and includes sectors radially movable relative to a geometric rotation axis, and circumferentially distributed one after the other. A plurality of strip-like elements is deposited in circumferential side by side relationship on the deposition surface set in the first deposition configuration, to form at least one component of at least one first crown structure. Setting of the deposition surface includes the actions of radially moving the sectors to give the deposition surface a predetermined diameter and carry out a relative movement between a central portion and axially external end portions of each sector to shape the deposition surface according to a predetermined curvature outline.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 13/993,156, filed Jun. 11, 2013, which is a National Phaseapplication based on PCT/IB2011/055272, filed Nov. 24, 2011, whichclaims the priority of Italian Patent Application No. MI2010A002377,filed Dec. 23, 2010, and the benefit of U.S. Provisional Application No.61/429,304, filed Jan. 3, 2011, all of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a process and a plant for buildingtyres for vehicle wheels. More specifically, the invention isparticularly addressed to manufacture of crown structures, in particularin production contexts in which building of the tyre takes place byassembling elementary semifinished products such as rubberised textileor metallic cords, strip-like elements formed starting from a continuousribbon-like element cut to size and comprising a plurality of textile ormetallic cords disposes parallel and adjacent to each other, and/orcontinuous elongated elements of elastomeric material circumferentiallywound into a plurality of mutually adjacent turns.

Description of the Related Art

A tyre for vehicle wheels generally comprises a carcass structureincluding at least one carcass ply having respectively opposite endflaps in engagement with respective annular anchoring structures,integrated into the regions usually identified as “beads”, defining theradially internal circumferential tyre edges.

Associated with the carcass structure is a belt structure comprising oneor more belt layers, placed in radially superposed relationship relativeto each other and to the carcass ply, provided with textile or metallicreinforcing cords having crossed orientation and/or substantiallyparallel to the circumferential extension direction of the tyre. Appliedat a radially external position to the belt layers is a tread band, madeof elastomeric material too, like other semifinished productsconstituting the tyre.

In addition, respective sidewalls of elastomeric material are applied atan axially external position to the side surfaces of the carcassstructure, each extending from one of the side edges of the tread banduntil close to the respective annular anchoring structure to the beads.In tyres of the “tubeless” type, an airtight coating layer, usuallyreferred to as “liner” covers the inner surfaces of the tyre.

To the aims of the present specification and the following claims, by“crown structure” of a tyre it is intended at least one belt structurehaving at least one belt layer or strip. More preferably, the crownstructure comprises a belt structure having at least one belt layer orstrip and a tread band.

In the specification and in the following claims the term “component” isunderstood as indicating any part of the tyre that is suitable toperform a function, or a portion thereof. Therefore, defined ascomponents are for example the liner, underliner, abrasion-proofelement, bead core, bead filler, carcass ply, belt strip, beltunder-layer, tread under-layer, sidewall inserts, sidewalls, tread band,reinforcing inserts.

In the present specification and in the following claims the term“strip-like element” is understood as indicating an elongated element ofelastomeric material of flattened shape and cut to size, including atleast one, preferably at least two textile or metallic reinforcing cordsthat are parallel to each other and to the longitudinal axis of theelongated element itself.

SUMMARY OF THE INVENTION

The Applicant has observed that it is possible to provide a forming drumcomprising a plurality of supporting elements having stiff surfaces forthe tyre components and disposed along the drum circumference, in whichthe support elements, considered in a diametrical section planecontaining the geometric axis of the drum, comprise central supportingportions and lateral supporting portions fastened thereto. The centralsupporting portions are movable by means of first actuating devicesbetween a first position at which the respective supporting elementsform a supporting surface parallel to the geometric axis of the drum,and at least one second position at which the supporting elements form aconvex surface. The first actuating devices are connected to the centralportions of the supporting elements for at least keeping them parallelto the geometric axis at least in the second position.

The Applicant has also observed that on a forming drum externally havinga substantially cylindrical deposition surface, a plurality ofstrip-like elements can be applied, which are disposed in mutuallyapproached relationship so as to form at least one first annularreinforcing layer on the forming drum itself set to a first workdiameter in which each of the applied strip-like elements on thedeposition surface subtends an arc of a circumference the width of whichis equal to a submultiple integer of the overall circumferentialextension of the deposition surface. Adjusting devices operating on theforming drum will subsequently expand it to a second work diametergreater than the first work diameter, while maintaining the depositionsurface thereof substantially cylindrical. The Applicant has alsoobserved that the forming drum may comprise consecutive circumferentialsectors radially movable upon command of the adjusting devices. Each ofthe circumferential sectors has comb-shaped end portions that are eachoperatively engaged in a comb-shaped end portion complementary theretocarried by a circumferentially adjacent circumferential sector.

The Applicant has noticed that basically each tyre size requires aspecific forming drum and in particular a specific auxiliary drum forforming one or more belt layers or a crown structure.

In fact, it is the Applicant's opinion that it is desirable for the beltlayers and/or other components of the crown structure to be madeaccording to a transverse outline which is as much as possible close toor coincident with the outline that the components must have in thefinished tyre.

While having verified that it is possible to use the same type offorming drum for two or more tyre sizes, the Applicant has howevernoticed that a process and apparatus as above described would requiremanagement of many forming drums for which a specific storehouse isnecessary.

The Applicant has felt the necessity to optimise management of theforming drums without being obliged to provide a specific storehouse ofbig sizes for forming drums having shapes and/or sizes different fromeach other, while at the same time ensuring the availability of aforming drum of appropriate sizes and shape for each type of tyre to beproduced.

The Applicant has found that by providing a forming drum in which thecurvature outline and therefore the deposition surface thereof can beconfigured in shape and sizes as a function of the size of the tyre tobe produced, the warehouse for the forming drums can be eliminated orgreatly reduced.

More particularly, in accordance with a first aspect, the inventionrelates to a process for building tyres for vehicle wheels, comprising:

-   -   making carcass structures;    -   making crown structures;    -   associating each carcass structure with each crown structure;    -   wherein making said crown structures comprises:    -   providing at least one first forming drum having a deposition        surface and comprising sectors radially movable relative to a        geometric rotation axis, and circumferentially distributed one        after the other;    -   setting the deposition surface in a first deposition        configuration;    -   depositing strip-like elements in circumferential side by side        relationship on the deposition surface set in the first        deposition configuration, so as to form at least one component        of at least one first crown structure;    -   wherein the action of setting said deposition surface comprises:    -   radially moving said sectors to give the deposition surface a        predetermined diameter;    -   carrying out a relative movement between a central portion and        axially external end portions of each sector, to shape the        deposition surface into a predetermined curvature outline.

The Applicant thinks that each component of the crown structure formedon the deposition surface already set to the desired depositionconfiguration, can advantageously have geometric features substantiallycoincident with those required in the finished tyre. The Applicant hasfurther ascertained that the components of the crown structure asobtained will not necessarily have to be submitted to importantdeformation actions for adapting the shape thereof to the designparameters during the work steps following their manufacture. Thusimportant qualitative improvements can be obtained in the final product.In addition, as the Applicant ascertained, a greater productionflexibility can be advantageously achieved, since a wide variety ofsizes and curvature outlines obtained using the same forming drum ismade available, while at the same time being limited the space notdirectly concerned with production, like that for storing the formingdrums, and being reduced the manufacturing and management costs for agreat number of forming drums.

In accordance with a second aspect, the invention relates to a plant forbuilding tyres for vehicle wheels, comprising:

-   -   a carcass-structure building line;    -   a crown-structure building line;    -   an assembling station for coupling each carcass structure to        each crown structure;    -   wherein the crown-structure building line comprises:    -   at least one first forming drum including sectors that are        radially movable relative to a geometric rotation axis, each of        them having at least one central portion and axially external        end portions that are radially movable relative to the central        portion, wherein said sectors are circumferentially distributed        one after the other so as to define a deposition surface;    -   devices for setting the deposition surface in at least one        deposition configuration;    -   devices for depositing strip-like elements in circumferential        side by side relationship on the deposition surface set in said        deposition configuration, so as to form at least one component        of at least one crown structure;    -   wherein said devices for setting the deposition surface        comprise:    -   radial-movement devices for moving the sectors so as to give the        deposition surface a predetermined diameter;    -   relative-movement devices for movement between the end portions        and central portion of each sector relative to the geometric        rotation axis, in order to shape the deposition surface into a        predetermined curvature outline.

This plant helps in making available a wide variety of curvatureoutlines and diametrical sizes of the deposition surface on the sameforming drum.

The present invention, in accordance with one of said aspects, can haveone or more of the preferred features hereinafter described.

In accordance with a possible embodiment, provision is made for:coupling said at least one first forming drum

with a handling device adapted to be activated for setting thedeposition surface to the first deposition configuration; decouplingsaid at least one first forming drum from the handling device beforecompleting formation of the first crown structure.

Also preferably provided is the action of coupling said at least onefirst forming drum again to the handling device, for setting thedeposition surface to a second deposition configuration.

Decoupling of the forming drum makes the handling device available forother operations.

For instance, the handling device decoupled from said at least one firstforming drum can be coupled to at least one second forming drum.Coupling of the handling device to said at least one second forming drumcan for example enable setting of the deposition surface and/orexecution of other processing operations on the second forming drumitself.

Preferably, coupling of the handling device to said at least one secondforming drum is carried out before coupling said at least one firstforming drum again to the handling device.

Meanwhile, the decoupled forming drum can be submitted to otherprocessing operations provided in the building cycle of the crownstructure.

For instance, at least one additional component of the crown structurecan be made on said at least one first forming drum decoupled from thehandling device.

Also provided can be at least transfer of said at least one firstforming drum from a first work location to at least one second worklocation.

At least one additional component of the crown structure can be made onsaid at least one first forming drum transferred to the second worklocation.

Provision is also preferably made for locking the deposition surface tothe respective deposition configuration during transfer of said at leastone first forming drum.

In particular flowing of different forming drums along the worklocations can be such managed that the simultaneous processing ofdifferent crown structures can be carried out.

Transfer of said at least one first forming drum from the first worklocation to said at least one second work location is carried out bysaid handling device.

A structural simplification of the plants and a reduction in theprocessing times can be thus achieved.

Preferably, carrying out of said relative movement comprises: lockingthe central portion of each sector relative to the geometric rotationaxis; moving the end portions of each sector relative to the geometricrotation axis.

Preferably, during said relative movement, the end portions of eachsector are moved towards the geometric rotation axis.

Thus a convex curvature outline can be given to the deposition surface.

Radial movement of the sectors is preferably carried out throughrespective sliders carried by the end portions of each sector.

It is also preferably provided that the radial movement of the sectorsbe carried out by driving at least one spiral-shaped cam in rotationaround said geometric rotation axis.

Thus a symmetric and timed movement of the end portions of each sectorcan be obtained.

In a preferred example of the invention the following actions are inaddition carried out: removing said at least one component of at leastone first crown structure from said at least one first forming drum;setting the deposition surface to a second deposition configuration;forming at least one component of at least one second crown structure onthe deposition surface.

Preferably, said at least one component of said at least one first crownstructure formed through deposition of strip-like elements incircumferential side by side relationship is a belt layer.

Preferably, at least one component of said at least one first crownstructure is made on said at least one first forming drum decoupled fromthe handling device.

According to a preferred embodiment, at least one component of the crownstructure is made on said at least one first forming drum transferred tosaid at least one second work location.

Preferably provided are central-portion locking devices, operating onthe central portion of each sector so as to lock it to a predeterminedwork position selected from a plurality of positions included between amaximum-contraction position and a maximum-expansion position.

Also provided can be end-portion locking devices, operating on the endportions of each sector for locking them to a predetermined workposition selected from a plurality of positions included between amaximum-contraction position and a minimum-contraction position relativeto the corresponding central portion.

Said relative-movement devices can be preferably activated concurrentlywith activation of the central-portion locking devices.

Said radial-movement devices can be preferably activated concurrentlywith activation of the end-portion locking devices.

The devices for setting the deposition surface preferably comprise atleast one handling device capable of being coupled in a removable mannerto said at least one first forming drum.

More particularly, said handling device can be preferably operativelycoupled to said radial-movement devices for determining activationthereof.

Said handling device can be operatively coupled to saidrelative-movement devices for determining activation thereof.

Preferably, said handling device can be operatively coupled to saidcentral-portion locking devices for operating deactivation thereof.

Preferably, the handling device is movable between a first work locationand at least one second work location for transfer of the forming drumbetween said first work location and said at least one second worklocation.

Preferably, the handling device comprises a robotized arm, preferably ananthropomorphous robotized arm.

In each sector, the end portions are preferably hinged on respectiveopposite ends of the central portion.

Each sector can further comprise intermediate portions each securedbetween one of the end portions and the central portion.

The radial-movement devices preferably comprise at least onespiral-shaped cam operatively engaging said sectors and drivable inrotation around the geometric axis to determine radial movement of thesectors.

Said spiral-shaped cam can be operatively in engagement with sliders,each carried by one of the end portions of one of said sectors.

Preferably the end portions of each sector are mutually interconnectedby a bridge structure.

Preferably, said bridge structure carries the end-portion lockingdevices.

The central-portion locking devices preferably comprise first brakesdrivable for unlocking the radial movement of the central portions.

More particular, each of said first brakes preferably operates between arod radial to the respective sector and a first runner slidably guidedrelative to the rod.

The end-portion locking devices can comprise second brakes drivable forunlocking the radial movement of the end portions relative to thecentral portions.

More particularly, each of said second brakes operates between a rodradial to the respective sector and a second runner slidably guidedrelative to said rod.

Also preferably provided are devices for selecting the depositionconfiguration to be given to the deposition surface as a function of thetype of tyre being processed.

The crown-structure building line preferably comprises a settinglocation provided for receiving said at least one first forming drum.

Said setting location comprises control devices that can be operativelycoupled to said end-portion locking devices, and can be activated forunlocking the radial movement of the end portions relative to thecentral portions.

Further features and advantages will become more apparent from thedetailed description of a preferred but not exclusive embodiment of aprocess and a plant for building tyres, in accordance with the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

This description will be set out hereinafter with reference to theaccompanying drawings, given by way of non-limiting example, in which:

FIG. 1 diagrammatically shows a top view of a plant for building tyresproduced in accordance with the present invention;

FIG. 2 shows a diametrical half-section of the forming drum;

FIG. 3 shows a section of a construction detail taken at one of thecircumferential sectors of the forming drum;

FIG. 4 shows the detail seen in FIG. 3 in a perspective view;

FIG. 5 shows a portion of the forming drum set to a diametricalmaximum-contraction condition with some parts removed for betteremphasising others;

FIG. 6 shows the drum of FIG. 5 set to a possible depositionconfiguration;

FIG. 7 is a fragmentary diametrical section of a tyre that can bemanufactured by the process and plant in reference.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the drawings, a plant for building tyres for vehiclewheels, provided for carrying into practice a process according to theinvention has been generally identified by reference numeral 1.

Plant 1 is intended for manufacturing tyres 2 (FIG. 7) essentiallycomprising a carcass structure 2 a having at least one carcass ply 3. Alayer of airtight elastomeric material or a so-called liner 4 can beapplied to the inside of the carcass ply/plies 3. Two annular anchoringstructures 5 each comprising a so called bead core 5 a carrying anelastomeric filler 5 b at a radially external position, are inengagement with respective end flaps 3 a of the carcass ply or plies 3.The annular anchoring structures 5 are integrated in the vicinity ofregions usually identified as “beads” 6, at which engagement betweentyre 2 and a respective mounting rim usually takes place.

A crown structure 7 is circumferentially applied around the carcassply/plies 3. The crown structure comprises a belt structure 8 having oneor more belt layers 8 a, 8 b and preferably a tread band 9circumferentially superposed on the belt structure 8.

So called “under-belt inserts” 8 c can be associated with the beltstructure 8 and they are each placed between the carcass ply/plies 3 andone of the axially opposite end edges of the belt structure 8.Alternatively or in addition to the under-belt inserts 8 c, annularinserts of elastomeric material and/or comprising cords or otherreinforcing elements can be radially superposed at least on the axiallyopposite end edges of the belt structure 8, and/or interposed betweenthe belt layers 8 a, 8 b, at least at said end edges.

Two sidewalls 10 each extending from the corresponding bead 6 to acorresponding side edge of the tread band 9, are applied to the carcassply/plies 3 at laterally opposite positions.

Plant 1 essentially comprises a carcass-structure building line 11,wherein the carcass structures 2 a of the tyres under production areformed. The crown structures 7 are produced in a crown-structurebuilding line, generally denoted at 12 in FIG. 1.

In an assembling station 100, operatively interposed between thecarcass-structure building line 11 and the crown-structure building line12 or operatively integrated into one of them, coupling of each carcassstructure 2 a to a respective crown structure 7 is carried out.

The carcass-structure building line 11 comprises a primary building drum14, on which the carcass structure 2 a of tyre 2 is preferably builtand/or assembled. The primary drum 14 preferably is a building drumhaving a substantially cylindrical shape.

The primary drum 14 can be operatively supported by a mandrel 15, arobotized arm, or another device enabling it to be, if necessary, drivenin rotation and/or suitably handled during application of the componentsof the carcass structure 2 a at the building station 11.

More particularly, the primary drum 14 is adapted to first receive liner4, if any, and subsequently the carcass ply or plies 3, so as to form acylindrical sleeve on the opposite end flaps of which the annularanchoring structures 5 are afterwards fitted. Turning-up of the endflaps 3 a of the carcass ply/plies 3 can be then carried out around theannular anchoring structures 5. Also provided may be application of atleast one sidewall portion 10 onto the primary drum 14, as well as atleast one abrasion-proof element, depending on the construction process.

In the example shown, the primary drum 14 and the carcass structure 2 asupported thereby, made in the form of a cylindrical sleeve, are pickedup by a first transfer member, diagrammatically shown in FIG. 1 anddenoted by arrow “T”, which member carries out transfer of them to theassembling station 100 for engaging the primary drum 14 on shapingdevices herein not shown as they can be made according to the disclosureof document WO 2010/064077 in the name of the same Applicant, forexample.

The crown-structure building line 12 is equipped with at least oneforming drum 18 usually also referred to as “auxiliary drum” that isadapted to be sequentially transferred between two or more worklocations 19, 20, 21 dedicated to manufacture of the crown structure.

In greater detail, in a possible embodiment at least one first worklocation 19 is dedicated to formation of the belt layer or layers 8 a, 8b, and/or to assembly of other components of the belt structure 8,according to a predetermined sequence. At least one second work location20 can be designed for formation of the tread band 9 on the beltstructure 8, at a radially external position. A third work location 21can be provided for applying additional annular inserts, such as theunder-belt inserts 8 c and/or at least one portion of the sidewalls 10in the continuation of the axially opposite edges of the tread band 9.

A possible second transfer member 22 movable from and to the main drum14 associated with the aforesaid shaping devices, carries out transferof the crown structure 8 from the forming drum 18 brought to theassembling station 100 too, to the carcass structure 2 a, at a radiallyexternal position thereto (FIG. 1). In known manner, when the crownstructure 8 is in a centred position relative to the carcass structure 2a, the latter is shaped in a toroidal configuration. The consequentradial expansion of the carcass ply/plies 3 leads the same to adhereagainst the inner surface of the crown structure 8, retained by thesecond transfer member 22.

Tyre 2 thus built can be removed from the primary drum 14 to besubmitted to a vulcanisation treatment and/or other processingoperations provided in the work cycle.

The forming drum 18 externally has a substantially cylindricaldeposition surface, formed with a plurality of sectors 24circumferentially distributed one after the other around a geometricrotation axis X of the forming drum.

To the aims of the present invention by “substantially cylindrical”deposition surface 23 it is intended a deposition surface the shape ofwhich corresponds to a solid of revolution defined by a generatrixhaving rectilinear development or arched development, as can be viewedfrom the accompanying drawings.

In other words, along the development of each sector 24, in aradial-section plane relative to the geometric rotation axis X, it ispossible to detect a curvature outline of the deposition surface 23.Preferably, this curvature outline is such that the difference between amaximum diameter Dmax measurable at a symmetry plane orthogonal to thegeometric rotation axis X of the forming drum 18, and a minimum diameterDmin findable at the axially opposite edges of the drum itself, isincluded between about 0 (cylindrical surface—straight curvatureoutline) and about 30% of the axial size E measurable between saidaxially opposite edges (FIG. 3).

In other words, the following relation is valid:

0=<(Dmax−Dmin)=>0.3*E.

Associated with each forming drum 18 are setting devices 25 that can bepreferably activated before starting manufacture of the first belt layer8 a on the forming drum 18, to set the deposition surface 23 in at leastone predetermined deposition configuration.

In greater detail, the deposition surface 23 can be preferably set inseveral deposition configurations, each of which can be selected eachtime in accordance with the geometric and/or dimensional features of thetyre under production.

Each sector 24 to this aim comprises at least one central portion 26 andat least two end portions 27 axially external relative to the centralportion 26 and extending in axially opposite directions relative to thelatter. The end portions 27 are preferably hinged on the central portion26, by hinging pins 28 for example that are in engagement with therespectively opposite ends of the central portion so as to be radiallymovable relative thereto.

In a possible variant not shown, each sector 24 can further compriseintermediate portions each secured between one of the end portions 27and the central portion 26 so as to make sectors 24, if necessary, moreadaptable to the required different curvature outlines.

The setting devices 25 essentially comprise radial-movement devices 29to move sectors 24 so as to give the deposition surface 23 apredetermined diameter, which cooperate with relative-movement devices30 for movement between the end portions and central portion of eachsector relative to the geometric rotation axis, in order to shape thedeposition surface into a predetermined curvature outline.

More particularly, the radial-movement devices 29 are adapted tosimultaneously cause translation of sectors 24 in a direction radial tothe geometric rotation axis X, so as to determine a variation in thediametrical sizes of the forming drum 18, starting from amaximum-contraction and minimum-curvature condition of the depositionsurface 23, in which sectors 24 can act in mutual abutment by means ofrespective circumferential shoulders 24a so as to give the depositionsurface 23 a continuous course.

The circumferential shoulders 24a of each sector 24 are preferablydefined at respective comb-shaped end portions 31 each of whichoperatively engages a comb-shaped end portion 31 geometricallycomplementary thereto, carried by a circumferentially adjacent sector24. In this manner, the deposition surface 23 advantageously keeps itssubstantially cylindrical conformation and a substantially continuousextension, i.e. without important discontinuities even following strongexpansion of the forming drum 18. Thus the forming drum 18 can be easilyadapted to processing of tyres with geometric and diametrical measureseven greatly different from each other.

Each sector 24 is carried by at least one or, as shown, one pair ofradial arms 32 preferably placed in the vicinity of respective axiallyopposite sides of the forming drum 18 and each operatively in engagementwith one of the end portions 27 of the respective sector 24. In apreferred solution, rotatably secured to each radial arm 32 is an end ofat least one connecting rod 33 the opposite end of which is hinged onthe corresponding end portion 27 of sector 24. Preferably, a bridgeportion 34 extends between the radial arms 32 and is rigidly engagedrelative to the same, so as to mutually interconnect the end portions 27of each sector 24.

At least one or, as shown, one pair of spiral-shaped cams 35 operativelyengage sectors 24 at respective sliders 35 each carried by therespective end portion of each sector 27. More particularly, each slider36 is preferably in engagement with one of said radial arms 32.

Each spiral-shaped cam 35 is fastened to a grip shank 37 coaxial withthe geometric rotation axis X, and it engages the sliders 36 of theradial arms 32 disposes on the same side of the forming drum 18.

At least one or, as shown, one pair of guide flanges 38 support sectors24 radially guiding them relative to the geometric rotation axis X bymeans of guide seats 39 slidably passed through by the respective radialarms 32. The guide flanges 38 are rotatably supported by the grip shank37 by rolling bearings 40, and at least one of them can carry stopdevices 41 to selectively enable and disable freedom of rotation of theguide flanges relative to the grip shank 37 . Said stop devices 41 arenot described in detail as they can be made following the description indocument WO2008/152453 in the name of the same Applicant, for example.

The spiral-shaped cams 35 lend themselves to rotate together with thegrip shank 37 relative to the guide flanges 38 and the circumferentialsectors 24. Thus it is possible to determine a simultaneous radialmovement of the circumferential sectors 24 and place them to a pluralityof positions included between a maximum-contraction position and amaximum-expansion position.

Central-portion locking devices 42 operate on the central portion 26 ofeach sector 24 so as to lock it to a predetermined work position thatcan be selected as a function of the geometrical and/or dimensionalfeatures of the tyre being processed.

More particularly, the central-portion locking devices 42 preferablycomprise first brakes 42 a each operating between a rod 43 radial to therespective sector 24 and a first runner 44 slidably guided relative torod 43. In a preferred embodiment the first runner 44 is fastened to theguide flanges 38 and is slidably passed through by rod 43 rigidlyconnected to the central portion 26 of the respective sector 24. Ingreater detail, formed on a radially external end portion of rod 43 is apair of extensions 45, rigidly connected to the central portion 26 ofthe respective sector 24.

Each of the first brakes 42 a, not shown in detail as they can be madein known manner, is operatively integrated into one of the first runners44 and, under rest conditions, is pushed against the rod 43 by one ormore spring members, to rigidly retain the central portion 26 of therespective sector 24. The first brakes 42 a are further adapted to besimultaneously deactivated, pneumatically for example, by overcoming theaction of the respective spring members, to free movement of rods 43relative to the first runners 44, so as to enable radial movement of thecentral portions of sectors 24.

To this aim, the first brakes 42 a can be connected to at least onefirst pneumatic-connection terminal 46 placed in the vicinity of thestop devices 40 for example, and laterally appearing from the formingdrum 18.

Also provided are end-portion locking devices 47 operating on the endportions 27 of each sector 24 to lock them to a predetermined workposition, selected from a plurality of positions included between amaximum-contraction position and a minimum-contraction position relativeto the corresponding central portion 26.

In greater detail, to this aim second brakes 47 a can be provided, eachof which operates between one of rods 43 and a second runner 48 slidablyguided relative to the rod itself. More particularly, in a preferredembodiment, a pair of second brakes 47 a is provided for each sector 24,which brakes are each associated with one of the end portions 27 andpreferably integrated into at least one respective second runner 48.Each second runner 48 is preferably fastened to the bridge structure 34of the respective sector 24 and is slidably passed through by saidextensions 45, radial to the respective sector 24.

Spring members push the second brakes 47 a of each sector 24 against therespective extensions 45, so as to lock the bridge structure 34 andrigidly retain the end portions 27 of the respective sector 24. Thesecond brakes 47 a are further adapted to be simultaneously deactivated,pneumatically for example, by overcoming the action of the respectivespring members, to make movement of the second runners 48 free along theextensions 45 so as to enable radial movement of the end portions 27 ofsectors 24 relative to the central portions 26.

To this aim, the second brakes 47 a can be connected to at least onesecond pneumatic-connection terminal 49 located at an end of the gripshank 37 for example, which is therefore provided with at least oneinner pipeline 50.

Operating in the crown-structure building line 12 is at least onehandling device 51 preferably comprising a preferably anthropomorphicrobotized arm, of the type provided with six or more movement axes,movable between the first and second work locations 19, 20 and/or otherlocations provided in the crown-structure building line 12. The handlingdevice 51 can be removably coupled to the forming drum 18 to transfer itbetween the work locations 19, 20, 21 provided in the crown-structurebuilding line 12, and it forms an integral part of the setting devices25 being operatively coupled to the radial-movement devices 29 and/orthe relative-movement devices 30.

More particularly, the handling device 51 engages the forming drum 18 atan end of the grip shank 37, preferably opposite to the secondpneumatic-connection terminal and can operate on the latter to drivealong in rotation the spiral-shaped cams 35 relative to the guideflanges 38. The handling device 51 can further be operatively coupledwith the central-portion locking devices 42, by at least one firstquick-fit pneumatic connection 52 for example, that can be operativelycoupled with the first pneumatic-connection terminal 46, through whichintroduction of compressed air to the brakes 42 a can be caused todetermine deactivation thereof.

Control devices 53 that can be operatively coupled to the end-portionlocking devices 47 can be provided in a setting location 54 operatingalong the crown-structure building line 12 to receive each forming drum18 for carrying out setting of the deposition surface 23 according tothe desired deposition configuration.

These control devices 53 may for example comprise at least one secondquick-fit pneumatic connection to be operatively coupled with the secondpneumatic-connection terminal 49 through which introduction ofcompressed air to the second brakes 47 a can be caused to determinedeactivation of the latter.

In accordance with a building process according to the invention, formanufacture of the crown structures 7, the forming drum 18 for instancepicked up from the assembling station 100 by the handling device 51 atthe end of building of a tyre, is provided to be engaged in the settinglocation 54 at which connection of the second brakes 47 a to acompressed-air feeding line is enabled, following coupling of the secondquick-fit pneumatic connection 53 with the second pneumatic-connectionterminal 49.

Selection devices not shown, comprising a programmable governing unitsupervising operation of the crown-structure building line 12 andpossibly of other parts of plant 1, carries out selection of a firstdeposition configuration to be given to the deposition surface 23selected as a function of the previously stored type of tyre beingprocessed.

The forming drum 18 at least partly contracted due to removal of thepreviously formed crown structure 7, can be, if necessary, submitted toa preliminary operation for initialising the position of sectors 24,implementing the maximum-contraction and minimum-curvature condition ofthe deposition surface 23. To this aim, the handling device 51 acts onthe grip shank 37 to drive the spiral-shaped cams 15 in rotation so asto bring back the end portions 27, if necessary, to theminimum-contraction position relative to the central portions 26. Thisaction is carried out after deactivation of the second brakes 47 a byintroduction of compressed air through the second pneumatic-connectionterminal 49, while the first brakes 42 a remain active on the respectiverods 43 to retain the central portions 26 during actuation of thespiral-shaped cams 35.

When the end portions 27 have reached to minimum-contraction position,deactivation of the first brakes 42 a through the firstpneumatic-connection terminal 46 is produced, concurrently withactivation of the second brakes 47 a. The handling device 51 thenrotates the grip shank 37, if necessary, in the opposite directionrelative to the preceding action, to bring the central portions 26 ofsectors 24 back to the maximum-contraction position. The end portions27, locked upon the action of the second brakes 47 a, follow the centralportions 26 in their motion of approaching the geometric rotation axisX.

When the above described possible initialising operation has beencompleted, the forming drum 18 is submitted to setting of the depositionsurface 23 to the first deposition configuration.

To this aim, while the first brakes 42 a are maintained inactive and thesecond brakes 47 a are maintained active, the handling device 51 acts onthe grip shank 37 to determine radial expansion of the depositionsurface 23, until sectors 24 reach a work position corresponding to apredetermined diameter of the deposition surface 23.

If the minimum-contraction position maintained by the end portions 27were not already in accordance with the desired curvature outline to begiven to the deposition surface 23, the spiral-shaped cams 35 can bedriven in rotation in the opposite way relative to the preceding action,concurrently with deactivation of the second brakes 47 a orre-activation of the first brakes 42 a for locking the central portions26 relative to the geometric rotation axis X. Thus a relative movementbetween the central portion 26 and the axially external end portions 27of each sector 24 is carried out to shape the deposition surface 23according to a predetermined curvature outline. More particularly, theend portions 27 move towards the geometric rotation axis X rotatingaround the respective hinging pins 28, so as to progressively increasethe curvature outline of the deposition surface 23 until the desiredvalue is reached.

Therefore the forming drum 18 has a diameter and a curvature outlinethat can be modulated in a manner independent of each other, to preparethe deposition surface 23 to process tyres geometrically different fromeach other.

When the desired deposition configuration has been reached, the handlingdevice 51 can remove the forming drum 18 from the setting location 54for proceeding with building of the crown structure 7.

The action of the first and second brakes 42 a, 47 a ensures that thedesired deposition configuration is maintained during the processingoperations and the transfer actions of the forming drum 18 between thework locations 19, 20, 21, until the end of the process. Possiblemodifications of the forming drum diameter during the process formanufacturing the crown structure 7, if required, can be at all eventscarried out through actuation of the radial-movement devices 29 uponcommand of the handling device 51, after deactivation of the firstbrakes 42 a.

In greater detail, the handling device 51 is adapted to retain the gripshank 37 to transfer the forming drum 18 to the first work location 19,at which at least one belt layer 8 a, 8 b or other component of thecrown structure 7 is produced by means of applicator devices 55preferably provided for depositing a plurality of strip-like elements Bin circumferential side by side relationship on the forming drum 18.

Said applicator devices 55, not described in detail for clearness ofexposition, can be accomplished following the description of patent U.S.Pat. No. 6,702,913 in the name of the same Applicant, for example.

The handling device 51 carries out appropriate positioning of theforming drum 18 at the applicator devices 55 and drives it in rotation,for example in a step-by-step movement, in timed relationship withdeposition of the individual strip-like elements B on the depositionsurface 23, so that said strip-like elements are applied in successionone adjacent to the other, each according to an orientation parallel toor suitably inclined relative to the geometric rotation axis X, untilthey cover the whole circumferential extension of the deposition surface23.

At least one second belt layer 8 b can be formed at a position radiallyexternal to the first belt layer 8 a, in the same manner as previouslydescribed but with the strip-like elements B preferably extending in acrossed orientation relative to those of the first belt layer 8 a.During manufacture of the second belt layer 8 b, the deposition surface23 of the forming drum 18 will be represented by the previously formedfirst belt layer 8 a.

Before and/or after manufacture of the belt layer/s 8 a, 8 b, at leastone annular insert of elastomeric material can be formed around thedeposition surface 23.

Said at least one annular insert may consist for example of part of thetread band 9, applied at a radially external position to the firstand/or second belt layer 8 a, 8 b, and/or at least part of the sidewalls10, each extending on the deposition surface 23, axially beyond theedges of said first and/or second belt layer 8 a, 8 b. One or moreannular inserts of elastomeric material can also form the under-beltinserts 8 c, applied onto the deposition surface 23 at a positionradially internal to the axially opposite edges of the belt layers 8 a,8 b.

Each annular insert can be advantageously made by spiralling at leastone continuous elongated element of elastomeric material, i.e. bywinding said continuous elongated element into substantiallycircumferential turns that are disposed in mutual side by siderelationship around the deposition surface 23.

To this aim, the second and/or third work location 20, 21 can compriseat least one delivery device 56, such as an extrusion die for example,distributing the continuous elongated element on the forming drum 18,while the latter is being driven in rotation around its geometricrotation axis X through the handling device 51, and conveniently movedby the latter to determine distribution of the turns in a manner adaptedto give a desired final conformation to the under-belt inserts 8 c, thetread band 9, and/or the sidewalls 10 being produced.

At least formation of the under-belt inserts 8 c should have to bepreferably carried out before setting of the deposition surface 23 tothe desired deposition configuration, i.e. with the deposition surfacein the maximum-contraction and minimum-curvature condition to whichmutual contact of sectors 24 in surface continuity relationshipcorresponds. Thus it is possible to eliminate the risk that thecontinuous elongated element applied directly in contact with theforming drum 18, may break during winding by effect of anomalousstresses caused by undesirable surface discontinuities of the formingdrum 18.

To this aim, the handling device 51 can carry out transfer of theforming drum 18 from the setting position 54 to the second and/or thirdwork location 20, 21 after the initialising operation.

When application of the under-belt inserts 8 c and/or possible otherelements radially internal to the belt layers 8 a, 8 b has beencompleted, the forming drum 18 can be transferred again to the settinglocation 54 to be set to the desired deposition configuration. Whensetting is over, the handling device 51 transfers the forming drum 18from the setting location 54 to the first work location 19 to form thebelt layer or layers 8 a, 8 b. Subsequently the handling device 51 cancarry out transfer of the forming drum 18 from the first work location19 to the second and/or third work location 20, 21, to determineformation of the tread band 9 and of at least one portion of thesidewalls 10.

When manufacture of the crown structure 7 has been completed, thehandling device 51 can transfer the forming drum to the assemblingstation 100, to enable engagement of the crown structure 7 by the secondtransfer member 22. Following radial contraction of sectors 24 of theforming drum 18, after unlocking of the first brakes 42 a, the formingdrum 18 can be axially slipped off and disengaged from the crownstructure 7 and be transferred again to the crown-structure buildingline 12 for starting manufacture of a new crown structure 7.

If required, the forming drum 18 can be engaged again in the settinglocation 54, before starting formation of a new crown structure 7 forsetting the deposition surface 23 to a second deposition configurationor bringing back the deposition surface 23 to the maximum-contractionand minimum-curvature condition before forming the under-belt inserts 8c designed to build a new crown structure 7. Alternatively, the formingdrum 18 can be directly transferred to one of the first, second or thirdwork location 19, 20, 21, in particular if the geometrical anddimensional features of the new crown structure 7 do not requiremodifications in the shape of the deposition surface 23.

The crown-structure building line 12 can be advantageously equipped withseveral forming drums, at least one first and one second forming drums18 a, 18 b, for example, to enable simultaneous processing of severalcrown structures 7.

Each of the forming drums 18, the first forming drum 18 a for example,can be advantageously decoupled from the handling device 51 beforeformation of the crown structure 7 on the first forming drum 18 itselfhas been completed, to enable it to be conveniently engaged, supportedand moved in the first, second and/or third work location 19, 20, 21, bya second robotized arm or device of other type (not shown), for example,so as to form one or more of the corresponding components of the crownstructure 7. Thus the handling device 51 decoupled from the firstforming drum 18 a will be available for engaging the second forming drum18 a so as to start formation of a new crown structure 7.

The handling device 51 itself will be in a position to be coupled withthe first forming drum 18 a again, to start a new work cycle andpossibly set the deposition surface 23 of the first forming drum itselfto a new deposition configuration.

1. A process for building tyres for vehicle wheels, comprising: makingcarcass structures (2 a); making crown structures (7); associating eachcarcass structure (2 a) with each crown structure (7); wherein makingsaid crown structures (7) comprises: providing at least one firstforming drum (18) having a deposition surface (23) and comprisingsectors (24) radially movable relative to a geometric rotation axis (X),and circumferentially distributed one after the other; setting thedeposition surface (23) to a first deposition configuration; depositingstrip-like elements (B) in circumferential side by side relationship onthe deposition surface (23) set in the first deposition configuration,so as to form at least one component of at least one first crownstructure (7); wherein the action of setting said deposition surface(23) comprises: radially moving said sectors (24) to give the depositionsurface (23) a predetermined diameter; carrying out a relative movementbetween a central portion (26) and axially external end portions (27) ofeach sector (24), to shape the deposition surface (23) into apredetermined curvature outline.
 2. A process as claimed in claim 1,further comprising: coupling said at least one first forming drum (18)to a handling device (51) adapted to be activated for setting thedeposition surface (23) to the first deposition configuration;decoupling said at least one first forming drum (18) from the handlingdevice (51) before completing formation of the first crown structure(7).
 3. A process as claimed in claim 2, further comprising the actionof coupling said at least one first forming drum (18) again to thehandling device (51), for setting the deposition surface (23) to asecond deposition configuration.
 4. A process as claimed in claim 2 or3, wherein the handling device (51) decoupled from said at least onefirst forming drum (18) is coupled to at least one second forming drum(18).
 5. A process as claimed in claim 4, wherein coupling of thehandling device (51) to said at least one second forming drum (18) iscarried out before coupling said at least first forming drum (18) againto the handling device (51).
 6. A process as claimed in claim 1, furthercomprising at least transfer of said at least one first forming drum(18) from a first work location (19) to at least one second worklocation (20).
 7. A process as claimed in claim 6, further comprisingthe action of locking the deposition surface (23) to the respectivedeposition configuration during transfer of said at least one firstforming drum (18).
 8. A process as claimed in claims 2 and 6, whereintransfer of said at least one first forming drum (18) from the firstwork location (19) to said at least one second work location (20) iscarried out by said handling device (51).
 9. A process as claimed inclaim 1, wherein carrying out of said relative movement comprises:locking the central portion (26) of each sector (24) relative to thegeometric rotation axis (X); moving the end portions (27) of each sector(24) relative to the geometric rotation axis (X).
 10. A process asclaimed in claim 1, wherein during said relative movement, the endportions (27) of each sector (24) are moved towards the geometricrotation axis (X).
 11. A process as claimed in claim 1, wherein theradial movement of the sectors (24) is carried out through respectivesliders (36) carried by the end portions (27) of each sector (24).
 12. Aprocess as claimed in claim 1, wherein the radial movement of thesectors (24) is carried out by driving at least one spiral-shaped cam(35) in rotation around said geometric rotation axis (X).
 13. A processas claimed in claim 1, comprising: removing said at least one componentof at least one first crown structure (7) from said at least one firstforming drum (18); setting the deposition surface (23) to a seconddeposition configuration; forming at least one component of at least onesecond crown structure (7) on the deposition surface (23).
 14. A processas claimed in claim 1, wherein said at least one component of said atleast one first crown structure (7) formed through deposition ofstrip-like elements (B) in circumferential side by side relationship isa belt layer (8 a, 8 b).
 15. A process as claimed in claim 2, wherein atleast one component of said at least one first crown structure (7) ismade on said at least one first forming drum (18) decoupled from thehandling device (51).
 16. A process as claimed in claim 6, wherein atleast one component of the crown structure (7) is made on said at leastone first forming drum (18) transferred to said at least one second worklocation (20).
 17. A plant for building tyres for vehicle wheels,comprising: a carcass-structure building line (2 a); a crown-structurebuilding line (12); an assembling station (13) for coupling each carcassstructure (2 a) to each crown structure (7); wherein the crown-structurebuilding line (12) comprises: at least one first forming drum (18)including sectors (24) that are radially movable relative to a geometricrotation axis (X), each of them having at least one central portion (26)and axially external end portions (27) that are radially movablerelative to the central portion, wherein said sectors (24) arecircumferentially distributed one after the other so as to define adeposition surface (23); devices for setting the deposition surface (23)in at least one deposition configuration; applicator devices (55) fordepositing strip-like elements (B) in circumferential side by siderelationship on the deposition surface (23) set in said depositionconfiguration, so as to form at least one component of at least onecrown structure (7); wherein said devices for setting the depositionsurface (23) comprise: radial-movement devices (29) for moving thesectors (24) so as to give the deposition surface (23) a predetermineddiameter; relative-movement devices (30) for movement between the endportions (27) and central portion (26) of each sector (24) relative tothe geometric rotation axis (X), in order to shape the depositionsurface (23) into a predetermined curvature outline.
 18. A plant asclaimed in claim 17, further comprising central-portion locking devices(42), operating on the central portion (26) of each sector (24) so as tolock it to a predetermined work position selected from a plurality ofpositions included between a maximum-contraction position and amaximum-expansion position.
 19. A plant as claimed in claim 17, furthercomprising end-portion locking devices (47), operating on the endportions (27) of each sector (24) for locking them to a predeterminedwork position selected from a plurality of positions included between amaximum-contraction position and a minimum-contraction position relativeto the corresponding central portion (26).
 20. A plant as claimed inclaim 18, wherein said relative-movement devices (30) can be activatedconcurrently with activation of the central-portion locking devices(42).
 21. A plant as claimed in claim 19, wherein said radial-movementdevices (29) can be activated concurrently with activation of theend-portion locking devices (47).
 22. A plant as claimed in claim 17,wherein said devices for setting the deposition surface (23) comprise atleast one handling device (51) capable of being coupled in a removablemanner to said at least one first forming drum (18).
 23. A plant asclaimed in claim 22, wherein said handling device (51) can beoperatively coupled to said radial-movement devices (29) for determiningactivation thereof.
 24. A plant as claimed in claim 22, wherein saidhandling device (51) can be operatively coupled to saidrelative-movement devices (30) for determining activation thereof.
 25. Aplant as claimed in claims 18 and 22, wherein said handling device (51)can be operatively coupled to said central-portion locking devices (42)for operating deactivation thereof.
 26. A plant as claimed in claims 22,wherein said handling device (51) is movable between a first worklocation (19) and at least one second work location (20) for transfer ofthe forming drum (18) between said first work location (19) and at leastone second work location (20).
 27. A plant as claimed in claim 22,wherein the handling device (51) comprises an anthropomorphous robotizedarm.
 28. A plant as claimed in claim 17, wherein in each sector (24) theend portions (27) are hinged on respective opposite ends of the centralportion (26).
 29. A plant as claimed in claim 17, wherein each sector(24) comprises intermediate portions each secured between one of the endportions (27) and the central portion (26).
 30. A plant as claimed inclaim 17, wherein the radial-movement devices (29) comprise at least onespiral-shaped cam (35) operatively engaging said sectors (24) anddrivable in rotation around the geometric axis to determine radialmovement of the sectors (24).
 31. A plant as claimed in claim 30,wherein said spiral-shaped cam (35) is operatively in engagement withsliders (36) each carried by one of the end portions (27) of one of saidsectors (24).
 32. A plant as claimed in claims 17 and 19, wherein theend portions (27) of each sector (24) are mutually interconnected by abridge structure (34).
 33. A plant as claimed in claim 32, wherein saidbridge structure (34) carries the end-portion locking devices (47). 34.A plant as claimed in claim 18, wherein the central-portion lockingdevices (42) comprise first brakes (42 a) drivable for unlocking theradial movement of the central portions (26).
 35. A plant as claimed inclaim 34, wherein each of said first brakes (42 a) operates between arod (43) radial to the respective sector (24) and a first runner (44)slidably guided relative to the rod.
 36. A plant as claimed in claim 19,wherein the end-portion locking devices (47) comprise second brakes (47a) drivable for unlocking the radial movement of the end portions (27)relative to the central portions (26).
 37. A plant as claimed in claim36, wherein each of said second brakes (47 a) operates between a rod(43) radial to the respective sector (24) and a second runner (48)slidably guided relative to said rod (43).
 38. A plant as claimed inclaim 17, further comprising devices for selecting the depositionconfiguration to be given to the deposition surface (23) as a functionof the type of tyre being processed.
 39. A plant as claimed in claim 17,wherein the crown-structure building line (7) comprises a settinglocation (54) provided for receiving said at least one first formingdrum (18).
 40. A plant as claimed in claims 19 and 39, wherein saidsetting location (54) comprises control devices (53) that can beoperatively coupled to said end-portion locking devices (47), and can beactivated for unlocking the radial movement of the end portions (27)relative to the central portions (26).